The subject matter disclosed herein relates to turbines and, more particularly, to the installation and retention of tangential dovetail buckets in a turbine rotor.
Some power plant systems, for example certain nuclear, simple cycle and combined cycle power plant systems, employ turbines in their design and operation. Some of these turbines include rotors (e.g., a drum rotor, a wheel and diaphragm rotor, etc.) employing a plurality of tangential dovetail buckets. These buckets are installed circumferentially about the rotor via a set of entry slots in the rotor posts. Once installed, due to the extreme environmental conditions which exist within the turbine during operation, these buckets must be secured and the entry slots must be sealed. Some systems rely on a closure bucket to secure the turbine buckets in place about the rotor and to seal the entry slot. During installation, this closure bucket is the last bucket to be installed in each given stage. Once the closure bucket is in place in the entry slot, a set of grub screws are used to securely affix the closure bucket to the rotor, thereby locking in the other turbine buckets and sealing the entry slot. However, these grub screws may be difficult to install and/or tighten, and the requisite grub screw holes which must be formed in the rotor to accommodate these grub screws may result in stress concentrations in the rotor.
Referring to FIG. 1, a schematic view of a known closure bucket 92 is shown connected to a rotor 20. Closure bucket 92 illustrated in FIG. 1 may include a bucket shank 90 and a vane/blade 91. Closure bucket 92 may be connected to rotor 20 via a set of grub screws 97 which are adapted to complement and connect with a set of apertures 21 in rotor 20, thereby securing closure bucket 92 to rotor 20.